Package making – Closing packages and filled receptacles – By means adapted to engage outturned seam of package cover
Reexamination Certificate
1999-03-19
2001-04-17
Kim, Eugene (Department: 3721)
Package making
Closing packages and filled receptacles
By means adapted to engage outturned seam of package cover
C053S374200, C053S375900
Reexamination Certificate
active
06216420
ABSTRACT:
The present invention relates to a device for heat sealing a tube of packaging sheet material filled with a pourable food product.
In particular, the present invention relates to a heat seal device which may suitably form part of packaging machines for continuously forming, from said tube of packaging material, aseptic sealed packages containing pourable food products.
Many pourable food products, such as fruit juice, pasteurized or UHT (ultra-high-temperature-processed) milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.
A typical example of such a package is the parallelepiped package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is formed by folding and sealing a strip-rolled packaging material. The rolled packaging material comprises layers of fibrous material, e.g. paper, covered on both sides with a thermoplastic material, e.g. polyethylene; and the side of the packaging material eventually contacting the food product in the package also has a layer of barrier material, e.g. an aluminium sheet, which in turn is covered with a layer of thermoplastic material.
As is known, such packages are produced on fully automatic packaging machines, on which a continuous tube is formed from the strip-fed packaging material; the strip of packaging material is sterilized on the packaging machine, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution; following sterilization, the sterilizing agent is removed, e.g. vaporized by heating, from the surfaces of the packaging material; and the strip of packaging material so sterilized is kept in a closed sterile environment, and is folded and sealed longitudinally to form a tube.
The tube is then filled with the sterilized or sterile-processed food product, and is sealed and cut at equally spaced cross sections into pillow packs, which are subsequently folded mechanically to form finished, e.g. substantially parallelepiped, packages.
Packaging machines of the above type are known in which the cross sections of the tube are sealed using heat seal devices substantially comprising a first and a second jaw movable towards each other in a direction crosswise to the tube axis. The jaws grip the tube under pressure at each cross section and heat seal the tube along two respective transverse sealing lines, between which the tube is subsequently cut to form the pillow packs and then the parallelepiped packages.
The first jaw comprises, at the front, an induction heating element defining two elongated straight active surfaces, which interact with and heat the tube material to the sealing temperature, and extend on opposite sides of and parallel to an intermediate plane perpendicular to the tube axis.
The second jaw comprises two supporting elements, which extend symmetrically on opposite sides of and parallel to the intermediate plane, face respective active surfaces of the first jaw, and in turn comprise, at the front, respective pressure pads made of plastic material. The pressure pads have respective flat front contact surfaces, which cooperate with respective active surfaces of the first jaw to heat seal the tube along respective sealing lines. More specifically, each front contact surface of the first jaw comprises a first flat longitudinal portion parallel to and facing a first longitudinal end portion of the front surface of the respective pressure pad; a second flat longitudinal portion facing an intermediate longitudinal portion of the front surface of the pressure pad and inclined with respect to the first portion so as to extend away from the pressure pad; and a third flat longitudinal portion facing a second longitudinal end portion of the front surface of the respective pressure pad, and which may either be parallel to the first portion or extend along a projection of the second portion.
Though widely used, known devices of the above type all suffer from one major drawback:poor efficiency. This is due to the front contact surfaces of the first jaw comprising an inclined portion, which, though necessary to ensure a local reduction in pressure on the tube and so expel the food product in the tube from the heat seal region, results in dispersion of the heat produced by the heating element, and therefore in reduced overall efficiency of the heat seal operation.
Another drawback of known devices of the above type lies in the pressure pads—which normally have a cross section substantially in the form of a rectangular trapezium—being housed inside respective U-shaped seats on the second jaw. Which seats, being defined by substantially straight lateral surfaces, fail to ensure adequate retention of the pads, particularly in the event of impact or external stress.
Moreover, when the jaws are gripped together, the pressure pads are compressed in a direction perpendicular to the supply path of the tube, and therefore deform elastically in a direction parallel to the supply path and project laterally with respect to the respective supporting elements of the second jaw, both towards the intermediate plane and, in the opposite direction, beyond the respective lateral end edges of the second jaw, along which the pressure pads are susceptible to cutting or damage serious enough to impair the efficiency and working life of the pads.
To eliminate the above drawback, it has been necessary to modify the standard structure of the second jaw by providing, along the lateral end edges of the second jaw, in an intermediate position and at the longitudinal seal of the tube, respective projections defining a support for the lateral portions of the pressure pads subject to in-service deformation. It is an object of the present invention to provide a device for heat sealing a tube of packaging sheet material filled with a pourable food product, designed to eliminate the aforementioned drawbacks in a straightforward, low-cost manner, and which, in particular, provides for a high degree of sealing efficiency.
The present invention also provides a device for heat sealing a tube of packaging sheet material filled with a pourable food product, which does not compulsorily require any structural alterations to the second jaw of the device. According to the present invention, there is provided a device for heat sealing a tube of packaging sheet material filled with a pourable food product and fed along a vertical supply path; said device comprising a first and a second jaw movable towards each other in a direction crosswise to said supply path to grip said tube under pressure at a respective cross section and to heat seal the tube along two respective transverse sealing lines; said first jaw comprising heating means having a pair of substantially straight active surfaces, which cooperate with said tube and extend on opposite sides of and parallel to an intermediate plane perpendicular to said supply path; said second jaw comprising a pair of pressure pads, which are housed in respective seats on the second jaw, extend on opposite sides of and parallel to said intermediate plane, and cooperate with respective said active surfaces of said heating means to heat seal said tube along respective said sealing lines;
characterized in that said active surfaces of said heating means have respective longitudinal projections; and in that each said pressure pad comprises a first longitudinal portion supported substantially rigidly in the respective said seat and facing a corresponding said projection; and a second longitudinal portion supported pliably in said seat and located adjacent to and on the opposite side of said first longitudinal portion to said intermediate plane.
According to another aspect of the invention, there is provided a device for heat-sealing a tube of packaging sheet material filled with pourable food product, wherein said second jaw comprises pressure means having at least one contact surface which cooperates with said heating means to heat seal said tube along said sealing section;
characterized in that said contact surface comprises a main contact
Karlsson Robert
Mazzetto Maurizio
Palmqvist Roland
Burns, Doane, Swecker & Mathis. L.L.P.
Kim Eugene
Tetra Laval Holdings & Finance S.A.
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